Kensington Palace announced Monday that Prince William and his wife, the Duchess of Cambridge, are expecting their third child.
The announcement released in a statement said the queen was delighted by the news.
William and Kate already have two children, Prince George and Princess Charlotte. Prince George, now four-years-old, was to start his first day of school on Monday. His sister, Princess Charlotte, turned two in May.
Kate suffered the same severe morning sickness when she carried her first two children, forcing the couple to make their baby news public perhaps earlier than they would have liked due to the necessity.
The Associated Press contributed to this report.